linux-kernel - [PATCH x86/mm 5/6] x86-32 ptrace get/putreg current task

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Message-Id: <20071129004205.B4BFD26F8E7@magilla.localdomain>
Date:	Wed, 28 Nov 2007 16:42:05 -0800 (PST)
From:	Roland McGrath <roland@...hat.com>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...e.hu>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: [PATCH x86/mm 5/6] x86-32 ptrace get/putreg current task


This generalizes the getreg and putreg functions so they can be used on the
current task, as well as on a task stopped in TASK_TRACED and switched off.
This lays the groundwork to share this code for all kinds of user-mode
machine state access, not just ptrace.

Signed-off-by: Roland McGrath <roland@...hat.com>
---
 arch/x86/kernel/ptrace_32.c |    8 ++++++++
 1 files changed, 8 insertions(+), 0 deletions(-)

diff --git a/arch/x86/kernel/ptrace_32.c b/arch/x86/kernel/ptrace_32.c
index 5aca84e..2607130 100644
--- a/arch/x86/kernel/ptrace_32.c
+++ b/arch/x86/kernel/ptrace_32.c
@@ -55,6 +55,12 @@ static int putreg(struct task_struct *child,
 		if (value && (value & 3) != 3)
 			return -EIO;
 		child->thread.gs = value;
+		if (child == current)
+			/*
+			 * The user-mode %gs is not affected by
+			 * kernel entry, so we must update the CPU.
+			 */
+			loadsegment(gs, value);
 		return 0;
 	case DS:
 	case ES:
@@ -104,6 +110,8 @@ static unsigned long getreg(struct task_struct *child, unsigned long regno)
 		break;
 	case GS:
 		retval = child->thread.gs;
+		if (child == current)
+			savesegment(gs, retval);
 		break;
 	case DS:
 	case ES:
-
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